Hi John,
To complement the description of Domenico, here is how my KR500
looked like from inside (picture 5&6):
http://www.pa3guo.com/kr500.html
I did clean it & apply greece over the balls. A photo of that
greece (the brand) you get when you go to http://www.pa3guo.com
and click on Rotors, then scroll down.
Not sure if my problem was your problem. What you describe
is different, mine was simply stuck. Anyway, all these rotors
need some treatment :-) Mine worked fine since then (6 years now).
Succes,
Henk, PA3GUO